The institute of electrical and electronics engineers (IEEE) 802.16e standard was adopted in 2007 as a sixth standard for international mobile telecommunication (IMT)-2000 in the name of ‘WMAN-OFDMA TDD’ by the ITU-radio communication sector (ITU-R) which is one of sectors of the international telecommunication union (ITU). An IMT-advanced system has been prepared by the ITU-R as a next generation (i.e., 4th generation) mobile communication standard following the IMT-2000. It was determined by the IEEE 802.16 working group (WG) to conduct the 802.16m project for the purpose of creating an amendment standard of the existing IEEE 802.16e as a standard for the IMT-advanced system. As can be seen in the purpose above, the 802.16m standard has two aspects, that is, continuity from the past (i.e., the amendment of the existing 802.16e standard) and continuity to the future (i.e., the standard for the next generation IMT-advanced system). Therefore, the 802.16m standard needs to satisfy all requirements for the IMT-advanced system while maintaining compatibility with a mobile WiMAX system conforming to the 802.16e standard.
Effective transmission/reception methods and utilizations have been proposed for a broadband wireless communication system to maximize efficiency of radio resources. An orthogonal frequency division multiplexing (OFDM) system capable of reducing inter-symbol interference (ISI) with a low complexity is taken into consideration as one of next generation wireless communication systems. In the OFDM, a serially input data symbol is converted into N parallel data symbols, and is then transmitted by being carried on each of separated N subcarriers. The subcarriers maintain orthogonality in a frequency dimension. Each orthogonal channel experiences mutually independent frequency selective fading, and an interval of a transmitted symbol is increased, thereby minimizing inter-symbol interference.
When a system uses the OFDM as a modulation scheme, orthogonal frequency division multiple access (OFDMA) is a multiple access scheme in which multiple access is achieved by independently providing some of available subcarriers to a plurality of users. In the OFDMA, frequency resources (i.e., subcarriers) are provided to the respective users, and the respective frequency resources do not overlap with one another in general since they are independently provided to the plurality of users. Consequently, the frequency resources are allocated to the respective users in a mutually exclusive manner. In an OFDMA system, frequency diversity for multiple users can be obtained by using frequency selective scheduling, and subcarriers can be allocated variously according to a permutation rule for the subcarriers. In addition, a spatial multiplexing scheme using multiple antennas can be used to increase efficiency of a spatial domain.
A sequence is widely used in a wireless communication system. In an OFDM/OFDMA system, a transmitter transmits respective elements constituting the sequence by mapping them to respective subcarriers. In general, the sequence preferably satisfies the following properties.
1) a correlation property suitable for providing excellent detection capability
2) a low peak-to-average power to ratio (PAPR) and cubic metric (CM) for maximizing efficiency of a power amplifier
3) a sufficient number of sequences for facilitating large-sized information transmission or cell-planning
4) a sequence that can be generated in a closed-form when a base station or a mobile station stores sequences in a look-up table format
The sequence is used for transmission of a preamble, a ranging channel, a pilot, a downlink/uplink control channel, a scrambling code, or the like, thereby capable of performing signal detection, channel estimation, multiplexing, or the like. When the sequence is generated, sequences allocated to a plurality of sub-blocks can be gathered so that the generated sequence has a desired length. In this case, even if each sub-block has an excellent sequence property, a sequence configured by gathering respective sequences to have a total length of the sequences may have a new property different from a property of each sequence.
Accordingly, there is a need for a method for generating a sequence with an excellent correlation property and a low PAPR and CM by maximizing the number of available sequences.